carb question

[canacudaa]

I bought my chally a week ago and it has a 318 with a holley 750 on it. does anyone think that a 750 is too big? Isnt a 600 or 650 much better? What are normal carb sizes for a 318?

[MEK-Dangerfield]

At first blush, yes I would say a 750 is too big. We need to know how your engine was built. If this is stock, or close to it, then I will say again that the 750 is too big. If your car isn't built radical with that 318, then, yes... a smaller carb would be in order. 

  Mike

[Oldschool]

I have run both a 340 and a 318 car.  I tried several carbs on both of them.  I had the best performance and streetability out of a Holley 650 Spreadbore Double Pumper.  Those worked great for me.

[MEK-Dangerfield]

I have run both a 340 and a 318 car.  I tried several carbs on both of them.  I had the best performance and streetability out of a Holley 650 Spreadbore Double Pumper.  Those worked great for me.

It seems in a few posts lately, the double-pumper has been given the nod. I totally agree. I have a Holley double-pumper, and the response is to die for. I hope I don't... but I have almost lost it a few times nailing it on the hiway. 

  Mike

[Rob C]

A stock 318 to a mildly modified can use no more than a 600 cfm carb.
If your teen is decently pumped up, a 650 is good.
Most case's, a 750 is allmost rediculas to have ontop for any reason except racing.
A smaller carb will increase in mileage and throttle response and off the line pep for sure. Unless the tuner of the 750 is real good about what hes doing......
IMO, Double pumpers are great with manuals, harder to tune for autos but not bad if you can feel the cars want for the secondarys.

[zerfetzen]

My signature explains the mild build on my 318, and I found at Edelbrock's website they have a guide, showing that a 600 cfm is appropriate for a stock engine ranging from 302-400 cubes, for whatever it's worth.

[71383bee]

A lot depends on the type of carb.  A Thermoquad runs in the 850 range and those were stock.  However, they are very sensitive to vacum signals and despite their immense size they will only give your motor what it can take.  The square bore carbs are a little different. 

For your teen the 750is probably too much unless it's really built well.  You would probably notice a quicker off idle response from a smaller carb. 

I love the 650 Mighty Demon on my 383 it is very snappy.  Personally i like mechanical secondaries versus vacum, but they are harder on mileage and are a bit more involved to tune.  it depends on your goals mostly though...

[Rob C]

Looking at the build below, the 600 is fine. A OE AVS (Small) is about 630 cfm as per the old Carter tech line and from the bin there done that, you'll like it alot. (AVS)
My first 318 had the Crane 272/284 - .454/.480 cam in it. 9.-1, torker II 600 cgm, headers w/360 heads. You can go real fast on the top end with that combo. Floored it until it stoped spining higher @ 6800 rpms. (Again, be there...)